Grindstone for manufacture of wood pulp



May 12, 1964 R. E. WAGNER GRINDSTONE FOR MANUFACTURE oF woon PULP Filed Aug. 16. 1961 HG2 5 L,

INVENTR.' Rudolf Ernsf Waner- BY w, zwlw RTTy.

United States Patent O 3,132,815 GRINJSTGNE FDR MANUFACTURE F WOOD PULP Rudolf Ernst Wagner, Stockholm, Sweden, asslgnor to Aktiebolaget Karlstads Mekaniska Werkstad, Karlstad, Sweden, a joint-stock company of Sweden Filed Ang. 16, 1961, Ser. No. 131,780 6 Claims. (Cl. 241-277) The present invention is related to grindstones to be used for wood pulp manufacture. It is known to provide the surface of such stones with grinding or sharpening furrows and in order to increase the quality of the wood fibres produced by the grinding it has been suggested to arrange a number of grooves in the surface of the stone, which grooves have a considerably larger breadth and depth than the sharpening furrows and which run parallel to or form a small angle with the rota-tion anis of the stone and thus run perpendicularly or almost perpendicularly to the direction of rotation of the stone. 'I'hese grooves have as purpose to collect the wood bres ground off by the grinding furrows so that these libres are not subject to any further grinding treatment from the grinding furrows. In the practice, however, it has turned out that such grooves, which are substantially perpendicular to the direction of rotation of the stone, are very rapidly obstructed due to the fact that the libres collected in the grooves together with splinters torn off and the like cannot be removed from the grooves sufliciently fast, but will be packed together in the grooves, whereby the output of fibres will decrease and the qual-ity of the pulp deteriorate.

Through the present invention these problems and disadvantages are eliminated and a grindstone is achieved, which with `a small power consumption gives an increased output of wood pulp of high quality. According to the invention this is lobtained with a giindstone, in which each of said grooves in the surface of the stone, which grooves have a considerably larger breadth and depth than the grinding furrows, runs circumferentially around the stone and forms along at least the larger pant of its length in the circumferential direction of the stone a small acute angle (up to with a plane perpendicular to the rotation axis of the stone, whereby these grooves will serve -as ydiverting grooves for the fibres ground olf by the grinding furrows. Dining operation each of said grooves will during each complete revolution of the stone be in permanent contact with the wood in the wood container of the grinding machine and the point of contact between the wood and the groovel will continuously move in a direction parallel-to the axis of rotation of the stone, i.e. in the longitudinal direction of the wood. The libres ground olf from the wood will consequently by means of the diverting grooves arranged in the stone be diverted as fast as possible from the grinding zone to a container for wood pulp arranged below the grinding stone. This has the Iadvantage that the danger of the libres being torn olf and shortened is considerably reduced. It ha-s also been proved by tests and analyses that a grinding with a grindstone according to the invention produces considerably longer and iiner fibres and a stronger wood pulp than a grinding with normal grindstones. The friction losses are also reduced `during the grinding due to which the power consumption decreases. A grindstone according to the invention can in practice be obtained by arranging the grooves, either in such a way that they form a continuous helix in the surface of the stone, or in such a Way lthat each groove forms a closed circle round the circumference of the stone, which circle lies in a plane which forms a small acute angle to the plane of rotation, which is perpendicular to the axis of the grindstone.

"ice

The enclosed drawings show by way of example two embodiments of the invention. FIG. 1 is Ia cross section through the lower part of the wood container and a part of a grindstone according to the invention. FIG. 2 shows one embodiment of the grindstone, in which the grooves form a continuous helix in the surface of the stone. FIG. 3 shows a grindstone, in which each groove forms a closed ring around the circumference of the stone.

In FIG. l, 1 designates the lower part of the wood container in which the wood 2, that shall be ground, is placed and in which the wood is by suitable mean-s' subject to a pressure so'that it is pressed towards the grindstone 3. The grindstone can consist of natural material, e.g.` sandstone, orpartially of a suitable synthetic material, which for instance is applied as a circumferential layer around a core of concrete or the like. According to the invention the circumferential surface of the 'stone 3 is provided with grooves 4 which run around the circumference of the stone. They should, however, not run in planes which are perpendicular to the axis of the grindstone but should yform a small angle to these planes. In the form shown in FIGURE 2 this has been achieved in that the grooves are arranged as a continuous helix in the circumferential surface of the stone so that grinding zones 5 of suitable breadth are formed between the separate turns of the groove. In the practice the grooves 4 may have a depth of about 20-25 mm. and a breadth of 15-20 mm. and the grinding Zones 5 may suitably have a breadth of -150 mm. in the axial direction of the stone. The grooves 4 form in the manner described above diverting ducts, which rapidly divert the libres from the grinding zones 5. Due to the :fact that the grooves 4 form an angle with the planes perpendicular to the axis of the stone, the libres produced in each grinding zone will rapidly arrive at or be picked up by a diverting duct and be collected and removed from the grinding zone 5 so that they are no longer subject to any further grinding action. In this way the advantages mentioned above are reached. 6 designates a spraying nozzle, by means of which the libres are washed away from the grinding zones and `out of the grooves, when these have left the wood container, down to a normal pulp container not shown in the drawing.

In the form of the invention shown in FIG. 3 the grooves 4 are separate from one another and arranged parallel to one another so that each groove It forms a closed ring around the circumference of the stone 3. Also in this case the grooves are arranged so that each groove lies in a plane which forms a small angle of up to 10 to 15 to the planes perpendicular to the axis of the stone. In this embodiment also, the fibers reduced in each grinding zone 5 rapidly arrive at or are picked up by a groove 4 and are thus collected and removed from the grinding Zone 5 by this action, so that they are no longer subjected to any further grinding action.

The embodiments of the invention described above and shown in the drawings have been chosen only as examples and they may of course be modied in several Ways in their details without detracting from the scope of the invention. y

What I claim is:

1. A grindstone for grinding logs to Wood pulp comprising a cylindrical body formed of a rigid abrasive composition, a plurality of grinding or sharpening furrows formed in the cylindrical surface of said body and disposed at an acute angle to the direction of the axis of said cylindrical body, and a plurality of grooves formed in said cylindrical surface and extending in a circumferential direction and intersecting said furrows, said circumferential grooves being considerably larger than said furrows in breadth and in depth, and each being oriented at least along the larger part of its length at a small acute angle of less than 15 to a plane perpendicular to the axis of said cylindrical body, whereby said grooves will, during the operation of said grindstone, collect and remove fibers separated from the logs by the cylindrical surface of said body and by said furrows.

2. A grindstone as claimed in claim 1, wherein the distance between adjacent grooves in the axial direction of the stone is from substantially 100 mm. to substantially 150 mm. v

3. A grindstone as claimed in claim 1, wherein said grooves have a depth of substantially 20 to 25 mrn. and a breadth of substantially 15 to 20 mm.

4. A grindstone for grinding logs to Wood pulp comprising a cylindrical body formed of a rigid abrasive composition, a plurality of grinding or sharpening furrows formed in the cylindrical surface of said body disposed at an acute angle to the direction of the axis of said cylindrical body, and a continuous helical groove formed in said cylindrical surface and disposed at an angle of substantially less than 15 to a plane perpendicular to the axis of said body and intersecting said furrows, said helical groove being considerably larger'than said furrows in breadth and in depth, whereby said helical groove Will, during the operation of said grindstone, collect and remove bers separated from the logs by the cylindrical surface and said body and by said furrows.

5. A grindstone for grinding logs to Wood pulp comprising a cylindrical body formed of a rigid abrasive composition, a plurality of grinding orsharpening furrows formed in the cylindrical surface of said body disposed at an acute angle to the direction of the axis of said cylindrical body, and a plurality of circumferential grooves formed in said cylindrical surface and each forming a closed ring, the plane of said ring being oriented at an angle of substantially less than 15 to a plane perpendicular to the axis of said body and intersecting said furroWs, whereby each of said circumferential grooves along the major part of its length will be disposed at a small angle to said perpendicular plane and will serve to collect and remove the fibers separated from said logs by the cylindrical surface of said body and by said turrows during the operation of said grindstone.

6. Apparatus for grinding logs to Wood pulp comprising a rotating cylindrical grindstone formed of a rigid abrasive composition, a log container disposed adjacent to the cylindrical surface of said grindstone, said cylindrical surface having a plurality of grinding or sharpening furrows disposed at an acute angle to the direction of the axis of said grindstone, and a plurality of grooves extending in a circumferential direction and intersecting said furrows, said circumferential grooves being considerably larger than said furrows in breadth and in depth, and each being oriented at least along the larger part of its length at a small acute angle of less than 15 to a plane perpendicular to the axis of said grindstone, whereby said grooves will, during the operation of said grindstone, collect and remove fibers separated from the logs by the cylindrical surface of said grindstone and by said furrows, and spray means disposed adjacent to said cylindrical surface at a point beyond said log container, in the direction of rotation thereof, for removing said bers from said grooves.

Hall Mar. 16, 1915 Mulhoiland V- Apr. 26, 1938 

1. A GRINDSTONE FOR GRINDING LOGS TO WOOD PULP COMPRISING A CYLINDRICAL BODY FORMED OF A RIGID ABRASIVE COMPOSITION, A PLURALITY OF GRINDING OR SHARPENING FURROWS FORMED IN THE CYLINDRICAL SURFACE OF SAID BODY AND DISPOSED AT AN ACUTE ANGLE TO THE DIRECTION OF THE AXIS OF SAID CYLINDRICAL BODY, AND A PLURALITY OF GROOVES FORMED IN SAID CYLINDRICAL SURFACE AND EXTENDING IN A CIRCUMFERENTIAL DIRECTION AND INTERSECTING SAID FURROWS, SAID CIRCUMFERENTIAL GROOVES BEING CONSIDERABLY LARGER THAN 